Silent chain, bush chain, and roller chain

ABSTRACT

A silent chain includes a first link, a second link, and coupling pins. The first link is configured from one or more first link plates that include a pair of first pin holes. The second link is configured from one or more second link plates that include a pair of second pin holes. The coupling pins are inserted through the respective first pin holes of the first link plate and the respective second pin holes of the second link plate. The coupling pins alternately couple the first link and the second link together along a chain drive direction so as to enable the first link and the second link to flex. Abrasive particles are embedded in inner peripheral faces at the pin holes of the first link plate and the second link plate.

CROSS-REFERENCE TO RELATED APPLICATIONS

The present application claims priority under 35 U.S.C. § 119 toJapanese Patent Application No. 2015-087472, filed Apr. 22, 2015,entitled “Silent Chain, Bush Chain, and Roller Chain.” The contents ofthis application are incorporated herein by reference in their entirety.

BACKGROUND

1. Field

The present disclosure relates to a silent chain, a bush chain, and aroller chain.

2. Description of the Related Art

As described in Japanese Unexamined Patent Application Publication No.2014-224556, for example, silent chains are configured by arranging linkplates, each including a pair of teeth and pin holes, so as to be offsetwith respect to each other in a length direction, inserting couplingpins through the pin holes so as to be rotatable therein and to couplethe link plates together, and also disposing guide plates, eachincluding a pair of pin fixing holes, at the side of the outermost linkplates, and press fitting the coupling pins into the pin fixing holes.As described in Japanese Unexamined Patent Application Publication No.2011-185297, bush chains are configured including an inner link,provided with a pair of parallel inner plates and a tube shaped bushinserted through the inner plates, and an outer link, provided with apair of outer plates disposed at the outside of the inner plates, and apin inserted through the outer plates and also inserted through theinside of the bush. The inner links and the outer links are alternatelycoupled together in an endless shape.

SUMMARY

According to a first aspect of the present invention, a silent chainincludes a first link, a second link, and coupling pins. The first linkis configured from one or more first link plates that include a pair offirst pin holes. The second link is configured from one or more secondlink plates that include a pair of second pin holes. The coupling pinsare inserted through the respective first pin holes of the first linkplate and the respective second pin holes of the second link plate. Thecoupling pins alternately couple the first link and the second linktogether along a chain drive direction so as to enable the first linkand the second link to flex. Abrasive particles are embedded in innerperipheral faces at the pin holes of the first link plate and the secondlink plate.

According to a second aspect of the present invention, a bush chainincludes a plurality of units. The plurality of units are coupledtogether in an endless shape and each include a pair of inner plates, abush, a pair of outer plates, and a coupling pin. The pair of innerplates each include a pair of bush holes. The bush is fixed to the bushhole and includes a pin hole. The pair of outer plates are each disposedat the outside of the respective inner plate. The coupling pin is fixedto the outer plates, and is inserted through and rotatable in the pinhole of the bush. Abrasive particles are embedded in an inner peripheralface at the pin hole of the bush.

According to a third aspect of the present invention, a roller chainincludes a plurality of units. The plurality of units are coupledtogether in an endless shape and each include a pair of inner plates, abush, a roller, a pair of outer plates and a coupling pin. The pair ofinner plates each include a pair of bush holes. The bush is fixed to thebush hole and includes a pin hole. The roller is rotatably supported atan outer periphery of the bush. The pair of outer plates are eachdisposed at the outside of the respective inner plate. The coupling pinis fixed to the outer plates, and is inserted through and rotatable inthe pin hole of the bush. Abrasive particles are embedded in an innerperipheral face at the pin hole of the bush.

According to a fourth aspect of the present invention, a silent chainincludes a first link, a second link, abrasive particles, and a couplingpin. The first link includes at least one first link plate that has apair of first pin holes. The second link includes at least one secondlink plate that has a pair of second pin holes. The abrasive particlesare embedded in inner peripheral faces of the first pin holes and thesecond pin holes. The coupling pin is inserted through one of the firstpin holes and one of the second pin holes so that the first link and thesecond link are alternately coupled along a chain drive direction inwhich the silent chain is to move so that the first link and the secondlink are flexible along the chain drive direction.

According to a fifth aspect of the present invention, a bush chainincludes bush chain units. The bush chain units are coupled together inan endless shape and each include a first inner plate, a second innerplate, a bush, abrasive particles, a first outer plate, a second outerplate, and a coupling pin. The first inner plate includes a pair offirst bush holes. The second inner plate includes a pair of second bushholes. The bush has a first end and a second end opposite to the firstend and is provided between the first inner plate and the second innerplate so that the first end and the second end are inserted through oneof the first bush holes and one of the second bush holes, respectively.The bush includes a pin hole extending from the first end to the secondend. The abrasive particles are embedded in an inner peripheral face ofthe pin hole. The first outer plate is disposed on an opposite side ofthe bush with respect to the first inner plate. The second outer plateis disposed on an opposite side of the bush with respect to the secondinner plate. The coupling pin is connected to the first outer plate andthe second outer plate and rotatably inserted through the pin hole ofthe bush.

According to a sixth aspect of the present invention, a roller chainincludes roller chain units. The roller chain units are coupled togetherin an endless shape and each include a first inner plate, a second innerplate, a bush, abrasive particles, a first outer plate, a second outerplate, and a coupling pin. The first inner plate includes a pair offirst bush holes. The second inner plate includes a pair of second bushholes. The bush has a first end and a second end opposite to the firstend and is provided between the first inner plate and the second innerplate so that the first end and the second end are inserted through oneof the first bush holes and one of the second bush holes, respectively.The bush includes a pin hole extending from the first end to the secondend. A roller is rotatably supported at an outer periphery of the bush.The abrasive particles are embedded in an inner peripheral face of thepin hole. The first outer plate is disposed on an opposite side of thebush with respective to the first inner plate. The second outer plate isdisposed on an opposite side of the bush with respective to the secondinner plate. The coupling pin is connected to the first outer plate andthe second outer plate and rotatably inserted through the pin hole ofthe bush.

BRIEF DESCRIPTION OF THE DRAWINGS

A more complete appreciation of the invention and many of the attendantadvantages thereof will be readily obtained as the same becomes betterunderstood by reference to the following detailed description whenconsidered in connection with the accompanying drawings.

FIG. 1 is a partial plan view illustrating part of a silent chain of afirst embodiment of the present application.

FIG. 2 is a side view illustrating part of a silent chain according tothe first embodiment of the present application.

FIG. 3A, FIG. 3B, and FIG. 3C are side views illustrating a guide plate,a link plate, and a pin.

FIG. 4A to FIG. 4C are cross-sections illustrating the inside of a pinhole of a link plate.

FIG. 5A and FIG. 5B are plan views illustrating part of a bush chain ofa second embodiment of the present application.

FIG. 6 is a side view illustrating part of a bush chain of the secondembodiment of the present application.

FIG. 7 is a graph illustrating a relationship of proportional chainstretch against the amount of Al of embedded alumina in an embodiment ofthe present application.

FIG. 8A is a graph illustrating a relationship between operating timeand external pitch of link plates in an embodiment of the presentapplication in which alumina is embedded, and FIG. 8B is a graphillustrating a relationship between operating time and external pitch oflink plates in a comparative example in which alumina is not embedded.

FIG. 9 is a cross-section illustrating a state in which abrasiveparticles have fallen off an inner peripheral face at a pin hole to formrecesses and protrusions.

DESCRIPTION OF THE EMBODIMENTS

The embodiments will now be described with reference to the accompanyingdrawings, wherein like reference numerals designate corresponding oridentical elements throughout the various drawings.

1. First Embodiment

Explanation follows regarding an embodiment of the present application,with reference to FIG. 1 to FIGS. 4A to 4C. FIG. 1 is a partial planview illustrating part of a silent chain of the embodiment. FIG. 2 is aside view thereof. The reference numerals 10 in the drawings indicatelink plates (in sets of four first link plates and three second linkplates). Each link plate 10 has a plate shape, and is formed with twoteeth 11 in a row along one side of the link plate 10 so as to projectout in substantially triangular shapes toward the side. Outside flanks11 a and inside flanks 11 b of the teeth 11 mesh with a sprocket (notillustrated in the drawings), and back faces 11 c of the teeth 11 slideagainst a chain guide (not illustrated in the drawings). A pair ofcircular pin holes 12 are respectively formed on center lines of therespective teeth 11. Abrasive particles of alumina (Al₂O₃), for example,are embedded in the inner peripheral face at each pin hole 12. Namely,as illustrated in FIG. 4A, lump shaped abrasive particles P1 areembedded in the inner peripheral face at the pin holes 12, in an atleast partially exposed state at the inner peripheral face. FIG. 4Billustrates a state in which powdered abrasive particles P2 are embeddedin an at least partially exposed state at the inner peripheral face, andFIG. 4C illustrates a state in which lump shaped abrasive particles P1and powdered abrasive particles P2 are embedded in an at least partiallyexposed state at the inner peripheral face. The particle size of thelump shaped abrasive particles P1 is 3 μm or smaller.

The reference numerals 20 in the drawings indicate guide plates. Theguide plates 20 are disposed on either side of the sprocket in thesprocket plate thickness direction, so as to prevent the silent chainfrom coming off the sprocket. Each guide plate 20 has a plate shape, andtwo protrusions 21 are formed in a row along one side of each guideplate 20 so as to project out toward the opposite side to the projectiondirection of the teeth 11. A pin hole 22 is formed inside eachprotrusion 21. The pitch of the pin holes 22 is the same as the pitch ofthe pin holes 12 of the link plates 10.

As illustrated in FIG. 1, plural of the link plates 10 are arranged suchthat their respective pin holes 12 are at different positions to eachother along the plate thickness direction, and coupling pins 30 areinserted through and rotatable in the respective pin holes 12. Endportions of the coupling pins 30 are fixed to the pin holes 22 of theguide plates 20 by press fitting, riveting, or the like. The couplingpins 30 are configured by circular steel rods with surface covering of ahard layer such as of VC or the like.

There is a manufacturing tolerance in an external pitch L of the linkplates 10, illustrated in FIG. 3B. The difference between the maximumvalue and the minimum value of the external pitch L of the link plates10, labeled a to d in FIG. 1, gives rise to a pitch step. During drivingof the silent chain configured as described above, when adjacent linkplates 10 flex with respect to each other, the abrasive particlesembedded in the inner peripheral faces at the pin holes 12 of the linkplates 10 are rubbed by the coupling pins 30 and fall out, so as tofunction as abrasive particles between the pin holes 12 and the couplingpins 30.

Link plates 10 having a short external pitch L are pulled with a largeforce along their length direction by the coupling pins 30, such thatthe pin holes 12 are scraped hard by the coupling pins 30. When thisoccurs, the inner peripheral faces at the pin holes 12 are ground by theabrasive particles, such that the external pitch L of the link plate 10is adjusted until it is similar to the external pitch of the other linkplates. Since the pitch step between the link plates with respect to thecoupling pins becomes smaller, load distribution across the link plates10 becomes more uniform, thereby enabling stretching of the silent chainto be suppressed as a result. Moreover, the grinding effect of employingabrasive particles of a specific particle size enables generation ofcoarse abraded grit to be suppressed from occurring during externalpitch adjustment. This thereby enables abraded grit to be reliablyprevented from causing adhesive wear between the coupling pins and theinner peripheral faces at the holes during chain driving, thus improvingthe wear characteristics of the chain itself.

2. Second Embodiment

FIG. 5A, FIG. 5B, and FIG. 6 illustrate a second embodiment of thepresent application, and illustrate an example in which the presentapplication is applied to a bush chain. The reference numerals 50 in thedrawings indicate inner plates. Each inner plate 50 has a flat plateshape formed with a semicircular shape at both ends, and bush holes 51are respectively formed on both sides of each inner plate 50. An endportion of a bush 60 is press-fitted into and fixed to each bush hole51.

Each bush 60 has a circular cylinder shape, with a hollow portion of thebush 60 configuring a pin hole 61. Abrasive particles of alumina(Al₂O₃), for example, are embedded in an inner peripheral face at eachpin hole 61. Coupling pins 70 are inserted through and rotatable in therespective pin holes 61.

Outer plates 80 are disposed at the two outside faces of the innerplates 50. Each outer plate 80 has a flat plate shape formed with asemicircular shape at each end, and pin fixing holes 81 are respectivelyformed at both ends of each outer plate 80. The pitch of the pin fixingholes 81 is the same as the pitch of the bush holes 51 of the innerplates 50. End portions of the coupling pins 70 are fixed to the pinfixing holes 81 by press fitting, crimping, or the like.

In the bush chain configured as described above, when adjacent innerplates 50 and outer plates 80 flex with respect to each other, theabrasive particles embedded in the inner peripheral faces at the pinholes 61 of the bushes 60 are rubbed by the coupling pins 70 and fallout, so as to function as abrasive particles between the pin holes 61and the coupling pins 70. When the inner plates 50 and the outer plates80 are pulled with a large force along their length direction by thecoupling pins 70, as illustrated in FIG. 5B, since each of the bushes 60is press-fitted into the respective bush holes 51, the two end portionsof the pin holes 61 are decreased in diameter, and central portions ofthe pin hole 61 bulge out in a barrel shape. There is accordingly nocontact with the coupling pins 70 at the central portions of the pinholes 61, and there is stronger contact at the two end portions of thepin holes 61. When the coupling pins 70 slide hard against theseportions of the pin holes 61, these portions are ground down by theabrasive particles embedded in the inner peripheral faces at the pinholes, thereby improving contact between the pin holes 61 and thecoupling pins 70. This thereby enables stretching of the bush chain tobe suppressed as a result. Moreover, the grinding effect of the abrasiveparticles enables the generation of coarse abraded grit to be suppressedfrom occurring, thereby enabling abraded grit to be prevented fromcausing adhesive wear during chain driving. This accordingly improvesthe wear characteristics of the chain itself.

In the embodiment described above is one in which the presentapplication is applied to a bush chain. However, application may also bemade to a roller chain in which rollers are rotatably supported by outerperipheral faces of the bushes 60.

In silent chains such as that illustrated in FIG. 1, alumina (Al₂O₃)with an average particle size of 3 μm was embedded in the innerperipheral faces at the pin holes 12 of the link plates 10 in varyingproportions, and each silent chain was entrained around a pair ofsprockets. Stretching of the silent chains was measured after operatingthe silent chains for a specific length of time. Moreover, the innerperipheral faces at the pin holes 12 were analyzed using an EnergyDispersive X-ray (EDX) analysis device, and the proportion of Al by masswas measured in a region from the outermost surface to the deepest pointat which Al was present (an abrasive particle layer). FIG. 7 illustratesthe obtained proportions of Al by mass together with the obtainedstretching of the silent chain.

As is apparent from FIG. 7, stretching of the silent chain decreasedwhen the proportion by mass of Al as Al₂O₃ was 2.5% or greater. Theseresults also confirmed that the proportion of abrasive particles in theabrasive particle layer of the link pin holes is preferably 5.0% by massor greater, and further reduces stretching.

Changes in the external pitch of the link plates 10 after operation werethen investigated. FIG. 8A illustrates the external pitches of the linkplates 10 of the silent chain of the present application, labeled a to din FIG. 1, prior to operation (0 h), and after being operated for 134hours (134 h). Prior to operation, the external pitches of link plates10 b and c were shorter than the external pitches of link plates a andd. After the inner peripheral faces at the pin holes 12 of the linkplates 10 were ground by the abrasive particles during operation, theexternal pitches of the link plates 10 b and c had widened to approachthe external pitches of the link plates 10 a and d. Accordingly, in thepresent application, the chain itself adjusted the pitch step so as tobecome substantially uniform when initially driven, without theperformance of any particular post-processing to correct variation inthe pitch. Stretching of the silent chain was accordingly suppressed.

FIG. 8B illustrates external pitch in a comparative example in whichalumina was not embedded in the inner peripheral faces at the pin holes12 of the link plates 10. As illustrated in FIG. 8B, there was a largeoverall widening of the external pitch between prior to operation (0 h)and after being operated for 134 hours (134 h), and there was also anincrease in the pitch step between the link plates. Namely, thisconfirms that more severe chain stretching occurs as a result ofvariation in the external pitch in ordinary silent chains that do notinclude abrasive particles.

The present application may be applied to silent chains, bush chains,and roller chains employed as drive transmission devices in all fieldsof transportation machinery, industrial machinery, and the like.

A silent chain of the present application includes a first linkconfigured from one or more first link plates that include a pair offirst pin holes, a second link configured from one or more second linkplates that include a pair of second pin holes, and coupling pins thatare inserted through the respective first pin holes of the first linkplate and the respective second pin holes of the second link plate. Thecoupling pins alternately couple the first link and the second linktogether along a chain drive direction so as to enable the first linkand the second link to flex. Abrasive particles are embedded in innerperipheral faces at the pin holes of the first link plate and the secondlink plate. Note that in the present application, “embed” refers to astate in which the abrasive particles are distributed on a substrate ina state in which the abrasive particles are at least partially, orcompletely, buried in the surface, and are embedded such that theabrasive particles fall out from the inner peripheral face at the pinhole due to contact with the coupling pin during chain driving.

When the silent chain of the present application is driven, the firstand second link plates mesh together with sprocket teeth, such that aflexing action takes place between the first and second link plates andthe coupling pin. Accompanying a pulling force acting on the chain dueto driving the sprocket, the inner peripheral faces at the pin holes andthe surface of the coupling pin slide against each other in a contactstate, pressed together in the drive direction, or the oppositedirection thereto. When this occurs, the abrasive particles embedded inthe inner peripheral faces at the pin holes of the link plates fall outdue to friction with the coupling pin, and fall into clearance betweenthe pin holes and the coupling pin surface. Lubricating oil is presentin the clearance, and the lubricating oil mixes with fine powder of thefallen abrasive particles to attain a state suitable for grinding. Notethat along the length direction of the respective coupling pins, load isapplied to link plates that have a short external pitch before load isapplied to other link plates, and for this reason, a larger load isapplied to link plates along the length direction of the coupling pinthat have a short external pitch than to the other link plates along thelength direction of the coupling pin. When the chain is flexed in thisstate, the pin holes of link plates with a short external pitch areheavily ground by the abrasive particles, while the pin holes of linkplates with a long external pitch are lightly ground, due to beingapplied with a smaller load than link plates with a short externalpitch. Due to the flexing action during chain driving, the pin holes ofthe respective link plates that are arranged along the length directionof the coupling pin are ground such that the pin holes attain uniformexternal pitch dimensions. Further grinding does not occur after theexternal pitch dimensions have been adjusted so as to be substantiallyuniform, since the load applied to the respective link plates has becomesubstantially uniform. The load acting on the link plates accordinglybecomes uniform at an early stage, thereby suppressing initialstretching of the silent chain. The grinding agent configured by thelubricating oil and the abrasive particles finely polishes the couplingpin, and smooths recesses and protrusions on cut surfaces of the pinholes formed by press punching, thereby enabling a marked improvement insubsequent chain stretching, and an increase in durability.

Note that the hardness of the abrasive particles is preferably the sameas or lower than the hardness of an outer peripheral face of thecoupling pin, and higher than the hardness of the inner peripheral facesat the pin holes of the link plates. Namely, the hardness of each memberis in the relationship coupling pin outer peripheral face>abrasiveparticles>pin hole inner peripheral faces. The inner peripheral faces atthe pin holes can accordingly be ground without causing wear of thecoupling pin, thereby enabling variation in pitch to be correctedwithout performing special processing.

Generally, an oxide grinding agent of alumina (Al₂O₃) is employed as theabrasive particles. These abrasive particles are embedded in the innerperipheral faces at the pin holes. The alumina is embedded in the pinholes of the link plates by barrel polishing. Alumina balls that areslightly smaller than the pin holes of the link plates, powdered alumina(Al₂O₃), and the link plates are placed in a barrel machine, and barrelpolishing is performed by finishing barrel polishing. Powdered aluminain slurry form and the alumina balls enter the pin holes and contact thepin hole due to rotation and rocking of the barrel polishing machine.When this occurs, the alumina balls drive the powdered alumina into thesurface of the pin holes. This thereby enables the powdered alumina tobe embedded in the inner peripheral faces at the pin holes. Carbideabrasive particles such as silicon carbide (SiC), or abrasive particlessuch as diamonds, may be employed instead of oxide abrasive particlessuch as alumina.

Embedding the abrasive particles in the pin holes forms an abrasiveparticle layer in which the particles of the abrasive particles aredistributed across the substrate in a surface layer region of the innerperipheral face at the pin holes. Investigation by the presentapplicants found that, for Al₂O₃ abrasive particles, the proportion ofabrasive particles in the abrasive particle layer is preferably 2.5% Alby mass or greater (Al was analyzed using Energy Dispersive X-ray (EDX)analysis, and this was employed as a proxy value for Al₂O₃). Thisenables stretching of the silent chain to be effectively suppressed.2.5% by mass of Al converts to about 5.0% by mass of Al₂O₃. Moreover,the average particle size of the alumina abrasive particles ispreferably 3 μm or smaller. Abrasive particles of this size give a finepolish to the sliding faces, and maintain an appropriate slidingenvironment between the pin and the inner faces at the pin holes,thereby enabling chain stretching to be suppressed. If, on the otherhand, the particle size of the abrasive particles is too large, chainstretching cannot be appropriately suppressed. This is due to thefollowing reason. When the abrasive particles fall off from the innerperipheral face, the larger the size of the abrasive particles, thedeeper the recesses left in the surface of the inner peripheral faceafter the abrasive particles have fallen off. Since the embeddedabrasive particles are distributed across the inner peripheral face,contiguous recesses are formed on the surface of the inner peripheralface, resulting in projections being formed between the recesses, asillustrated in FIG. 9. If such projections are rubbed by large sizeabrasive particles, cutting (snapping off of the projections) occursinstead of grinding, generating large size abraded grit. This leads toadhesive wear occurring, such that chain stretching cannot beappropriately suppressed. Thus as long as the abrasive particles ofalumina are 3 μm or smaller, then the abraded grit is also 3 μm orsmaller, enabling the occurrence of adhesive wear to be suppressed. Asmall particle size for the abrasive particles is accordinglypreferable, since the smaller the particle size of the abrasiveparticles, the smaller the particle size of the abraded grit generated.The abrasive particles may be a fine powder of 1 μm or smaller, orabrasive particles of different particle sizes may be mixed together, aslong as they are particles of 3 μm or smaller. Note that similar applieswhen employing other abrasive particles, such as SiC or other grindingagents.

Moreover, a bush chain the present application includes plural unitsthat are coupled together in an endless shape. Each unit includes a pairof inner plates each including a pair of bush holes, a bush that isfixed to the bush hole and includes a pin hole, a pair of outer platesthat are each disposed at the outside of the respective inner plate, anda coupling pin that is fixed to the outer plates, and is insertedthrough and rotatable in the pin hole of the bush. Abrasive particlesare embedded in an inner peripheral face at the pin hole of the bush.

In the bush chain of the present application, when adjacent inner platesand outer plates flex with respect to each other, the abrasive particlesembedded in the inner peripheral face at the pin hole of the bush fallout due to friction with the coupling pin, and function as abrasiveparticles between the pin hole and the coupling pin. Generally, the bushis press fitted into the bush holes of the inner plates, and thediameter at the two end portions of the pin holes in the bush is reducedby an interference amount. The two end portions of the coupling pinsaccordingly contact the inner peripheral face of the bushes more firmlythan central portions of the coupling pins. According to the presentapplication, the inner peripheral faces at the two end portions of thepin holes are ground by the abrasive particles, thereby enablingstretching of the bush chain to be suppressed due to being able to makecontact between the coupling pin and the bush inner peripheral faceuniform. Moreover, the grinding effect of employing abrasive particlesof a specific particle size suppresses generation of coarse abraded gritfrom occurring, thereby enabling the occurrence of adhesive wear byabraded grit to be prevented, and thus improving the wearcharacteristics. The above numerical limits for the silent chain mayalso be applied to the bush chain. The present application may also beapplied to a roller chain in which rollers are rotatably provided at theouter periphery of the bushes of the bush chain.

Obviously, numerous modifications and variations of the presentinvention are possible in light of the above teachings. It is thereforeto be understood that within the scope of the appended claims, theinvention may be practiced otherwise than as specifically describedherein.

What is claimed is:
 1. A silent chain comprising: a first linkconfigured from one or more first link plates that include a pair offirst pin holes; a second link configured from one or more second linkplates that include a pair of second pin holes; and coupling pins thatare inserted through the respective first pin holes of the first linkplate and the respective second pin holes of the second link plate,wherein the coupling pins alternately couple the first link and thesecond link together along a chain drive direction so as to enable thefirst link and the second link to flex, and abrasive particles areembedded in inner peripheral faces at the pin holes of the first linkplate and the second link plate.
 2. The silent chain according to claim1, wherein: the hardness of an outer peripheral face of the coupling pinis higher than the hardness of the inner peripheral face at the pinhole; and the hardness of the abrasive particles is lower than thehardness of the outer peripheral face of the coupling pin, and higherthan the hardness of the inner peripheral face at the pin hole.
 3. Thesilent chain of claim 1, wherein the abrasive particles are Al₂O₃, andthe proportion of Al by mass in a region from the outermost surface ofthe pin hole to the deepest location at which Al is present is 2.5% bymass or greater.
 4. The silent chain of claim 1, wherein the averagesize of the abrasive particles is 3 μm or smaller.
 5. A silent chaincomprising: a first link including at least one first link plate thathas a pair of first pin holes; a second link including at least onesecond link plate that has a pair of second pin holes; abrasiveparticles embedded in inner peripheral faces of the first pin holes andthe second pin holes; and a coupling pin inserted through one of thefirst pin holes and one of the second pin holes so that the first linkand the second link are alternately coupled along a chain drivedirection in which the silent chain is to move so that the first linkand the second link are flexible along the chain drive direction.
 6. Thesilent chain according to claim 5, wherein a hardness of an outerperipheral face of the coupling pin is higher than a hardness of theinner peripheral faces of the first pin holes and the second pin holes,and wherein a hardness of the abrasive particles is lower than thehardness of the outer peripheral face of the coupling pin, and higherthan the hardness of the inner peripheral faces of the first pin holesand the second pin holes.
 7. The silent chain according to claim 5,wherein the abrasive particles comprise Al₂O₃, and wherein a proportionof Al by mass in a region from outermost surfaces of the first pin holesand the second pin holes to a deepest location at which Al is present is2.5% by mass or greater.
 8. The silent chain according to claim 5,wherein an average size of the abrasive particles is 3 μm or smaller. 9.A bush chain comprising a plurality of units that are coupled togetherin an endless shape and each include: a pair of inner plates eachincluding a pair of bush holes; a bush that is fixed to the bush holeand includes a pin hole; a pair of outer plates that are each disposedat the outside of the respective inner plate; and a coupling pin that isfixed to the outer plates, and is inserted through and rotatable in thepin hole of the bush, wherein abrasive particles are embedded in aninner peripheral face at the pin hole of the bush.
 10. The bush chain ofclaim 9, wherein: the hardness of an outer peripheral face of thecoupling pin is higher than the hardness of the inner peripheral face atthe pin hole; and the hardness of the abrasive particles is lower thanthe hardness of the outer peripheral face of the coupling pin, andhigher than the hardness of the inner peripheral face at the pin hole.11. The bush chain of claim 9, wherein the abrasive particles are Al₂O₃,and the proportion of Al by mass in a region from the outermost surfaceof the pin hole to the deepest location at which Al is present is 2.5%by mass or greater.
 12. The bush chain of claim 9, wherein the averagesize of the abrasive particles is 3 μm or smaller.
 13. A bush chaincomprising: bush chain units coupled together in an endless shape andeach comprising: a first inner plate including a pair of first bushholes; a second inner plate including a pair of second bush holes; abush having a first end and a second end opposite to the first end andprovided between the first inner plate and the second inner plate sothat the first end and the second end are inserted through one of thefirst bush holes and one of the second bush holes, respectively, thebush including a pin hole extending from the first end to the secondend; abrasive particles embedded in an inner peripheral face of the pinhole; a first outer plate disposed on an opposite side of the bush withrespect to the first inner plate; a second outer plate disposed on anopposite side of the bush with respect to the second inner plate; and acoupling pin connected to the first outer plate and the second outerplate and rotatably inserted through the pin hole of the bush.
 14. Thebush chain according to claim 13, wherein a hardness of an outerperipheral face of the coupling pin is higher than a hardness of theinner peripheral face of the pin hole, and wherein a hardness of theabrasive particles is lower than the hardness of the outer peripheralface of the coupling pin, and higher than the hardness of the innerperipheral face of the pin hole.
 15. The bush chain according to claim13, wherein the abrasive particles comprise Al₂O₃, and wherein aproportion of Al by mass in a region from an outermost surface of thepin hole to a deepest location at which Al is present is 2.5% by mass orgreater.
 16. The bush chain according to claim 13, wherein an averagesize of the abrasive particles is 3 μm or smaller.
 17. A roller chaincomprising a plurality of units that are coupled together in an endlessshape and each include: a pair of inner plates each including a pair ofbush holes; a bush that is fixed to the bush hole and includes a pinhole; a roller that is rotatably supported at an outer periphery of thebush; a pair of outer plates that are each disposed at the outside ofthe respective inner plate; and a coupling pin that is fixed to theouter plates, and is inserted through and rotatable in the pin hole ofthe bush, wherein abrasive particles are embedded in an inner peripheralface at the pin hole of the bush.
 18. The roller chain of claim 17,wherein: the hardness of an outer peripheral face of the coupling pin ishigher than the hardness of the inner peripheral face at the pin hole;and the hardness of the abrasive particles is lower than the hardness ofthe outer peripheral face of the coupling pin, and higher than thehardness of the inner peripheral face at the pin hole.
 19. The rollerchain of claim 17, wherein the abrasive particles are Al₂O₃, and theproportion of Al by mass in a region from the outermost surface of thepin hole to the deepest location at which Al is present is 2.5% by massor greater.
 20. The roller chain of claim 17, wherein the average sizeof the abrasive particles is 3 μm or smaller.
 21. A roller chaincomprising: roller chain units coupled together in an endless shape andeach comprising: a first inner plate including a pair of first bushholes; a second inner plate including a pair of second bush holes; abush having a first end and a second end opposite to the first end andprovided between the first inner plate and the second inner plate sothat the first end and the second end are inserted through one of thefirst bush holes and one of the second bush holes, respectively, thebush including a pin hole extending from the first end to the secondend, a roller being rotatably supported at an outer periphery of thebush; abrasive particles embedded in an inner peripheral face of the pinhole; a first outer plate disposed on an opposite side of the bush withrespective to the first inner plate; a second outer plate disposed on anopposite side of the bush with respective to the second inner plate; anda coupling pin connected to the first outer plate and the second outerplate and rotatably inserted through the pin hole of the bush.
 22. Theroller chain according to claim 21, wherein a hardness of an outerperipheral face of the coupling pin is higher than a hardness of theinner peripheral face of the pin hole, and wherein a hardness of theabrasive particles is lower than the hardness of the outer peripheralface of the coupling pin, and higher than the hardness of the innerperipheral face of the pin hole.
 23. The roller chain according to claim21, wherein the abrasive particles comprise Al₂O₃, and wherein aproportion of Al by mass in a region from an outermost surface of thepin hole to a deepest location at which Al is present is 2.5% by mass orgreater.
 24. The roller chain according to claim 21, wherein an averagesize of the abrasive particles is 3 μm or smaller.